A conventional liquid crystal display panel, as shown in FIG. 1, generally includes an array substrate 110, a color filter substrate 120 and a liquid crystal layer there-between. In order to keep the gap between the array substrate 110 and the color filter substrate 120 consistent, some liquid crystal display panels also include a plurality of spacers including a main spacer 131 and a sub-spacer 132 for keeping the gap uniform.
Since the sizes of the main spacer and the sub-spacer on the horizontal projection are relatively close to each other and requirements on the main spacer and sub-spacer of a general liquid crystal display panel are different, it is necessary to identify the main spacer and the sub-spacer. However, none of the solutions of the prior art can be used to easily identify the main spacer and the sub-spacer.